强剪切轧制调控6XXX铝合金板材织构与成形性能的机理研究

A shear strain component with the same magnitude of the normal strain components is introduced into plate rolling by the horizontal shift and velocity ratio change between rollers, i.e. the so-called shear rolling, to develop crystallographic texture characterized by near {111} components, which means improved formability of sheets, in rolled 6XXX aluminum alloy sheets for automobile body. Fundamental research about texture design, texture evolution during shear rolling and solution heat treatment are included in the present project. Firstly, deformation history related crystal plasticity model should be established to investigate the influence of two sequential and reversal shears on the development of deformation textures. By modification of a laboratory rolling mill, experimental shear rolling of 6XXX series aluminum alloy will be carried out to characterize the shear rolling texture components. The quantitative evolution of the near {111} components and other components during shear rolling will be revealed by the above mentioned research work. Secondly, with the thermal and dynamical calculation, the boundary related precipitation behavior of dispersoids containing the added transition metal elements is to be investigated. The influence of the above boundary-related dispersoids on the migration behavior of grain boundaries during solution heat treatment should also be investigated. The influence of transition metal elements on the evolution of texture (recrystallization textures) during solution heat treatment of shear rolled 6XXX series aluminum alloy sheets will be revealed with the above research work. And the results will help developing texture components with high formability by solution heat treatment. Finally, the influence of shear rolling and recrystallization texture components on the formability of sheets is to be numerically investigated. Based on the investigation results, a texture design for excellent formability of shear rolled 6XXX series aluminum alloy sheets will be established, which will help developing shear rolling prototype technique to develop designed crystallographic textures..

为提高6系铝合金板材成形性能，提出通过轧机上下轧辊错位及辊速比的调整，实现轧制过程中引入与主应变相当的剪切应变，即所谓的强剪切轧制形成以近{111}面织构为主的高成形性织构组态，提高板材的成形性能。首先，建立基于晶体塑性理论且与塑性变形历史相关的织构演变模型，研究强剪切轧制方式下两个先后反方向剪切应变历史对形变织构的影响；在此基础上改造实验轧机，开展强剪切轧制实验，研究强剪切条件下织构特征，揭示强剪切轧制方式下特征织构演变规律。其次，以热力学、动力学计算为指导，研究合金中微量过度金属元素均匀化、热轧过程中形成的弥散相结构、分布与界面特征的关系，探求这些弥散相对固溶热处理过程晶界迁移行为的影响，揭示微量过度金属元素对强剪切轧制6XXX系铝板固溶过程织构转变的影响。最后，研究强剪切轧制织构特征对成形性能的影响，建立相应的织构优化设计方法，为强剪切轧制制备高成形性铝合金板材织构调控奠定基础。

为提高Al-Mg-Si系铝合金板材成形性能，本项目提出通过轧机上下轧辊错位及辊速比的调整，实现轧制过程中引入与主应变相当的剪切应变，即所谓的强剪切轧制形成以近{111}面织构为主的高成形性织构组态，提高板材的成形性能。首先，建立基于晶体塑性理论且与塑性变形历史相关的织构演变模型，研究强剪切轧制方式下两个先后反方向剪切应变历史对形变织构的影响，发现剪切应变和正应变的比值在0.7以上可以形成强的(111)织构；在此基础上改造实验轧机，开展强剪切轧制实验，研究强剪切条件下织构特征，揭示强剪切轧制方式下特征织构演变规律，在获得强（11）织构的同时，保证了板材的平直度。其次，研究合金中微量过度金属元素均匀化、热轧过程中形成的弥散相、分布与再结晶形核的关系，揭示了强剪切轧制板材固溶处理过程织构演变的规律，发现10分钟内完成固溶处理可以较好的实现固溶和强（111）织构的协同。同时还提出了适当降低淬火冷却速度抑制淬火自由空位浓度，从而抑制自然时效行为，提高成形性能和烤漆硬化速率。最后，研究强剪切轧制织构特征对成形性能的影响，建立相应的织构优化设计方法，为强剪切轧制制备高成形性铝合金板材织构调控奠定基础，实现铝合金板材R值达到1.1以上。